<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="./05.js" async></script>
</head>
<body>
  <span>请输入一个数字:</span>
  <!-- 用户的输入 -->
  <input type="text" name="input" id="input">
  <!-- 计算的按钮 -->
  <button id="run">计算</button>
  <!-- 计算的输出 -->
  <p id="out"></p>
</body>
</html>